/* ===================================
   CSS Variables & Reset
   =================================== */
:root {
    /* Colors */
    --primary-color: #0078D4;
    --primary-dark: #005A9E;
    --secondary-color: #50E6FF;
    --accent-color: #8661C5;
    --success-color: #00C851;
    --background: #0F0F1E;
    --surface: #1A1A2E;
    --surface-light: #252541;
    --text-primary: #FFFFFF;
    --text-secondary: #B8B8D1;
    --text-muted: #6E6E8F;
    --border-color: #2D2D44;
    
    /* Gradients */
    --gradient-primary: linear-gradient(135deg, #0078D4 0%, #50E6FF 100%);
    --gradient-accent: linear-gradient(135deg, #8661C5 0%, #50E6FF 100%);
    --gradient-success: linear-gradient(135deg, #00C851 0%, #50E6FF 100%);
    --gradient-overlay: linear-gradient(180deg, rgba(15, 15, 30, 0) 0%, rgba(15, 15, 30, 0.8) 100%);
    
    /* Typography */
    --font-primary: 'Poppins', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --font-display: 'Playfair Display', serif;
    
    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;
    --spacing-2xl: 4rem;
    
    /* Border Radius */
    --radius-sm: 8px;
    --radius-md: 16px;
    --radius-lg: 24px;
    
    /* Shadows */
    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.1);
    --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.2);
    --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.3);
    --shadow-glow: 0 0 40px rgba(80, 230, 255, 0.3);
    
    /* Transitions */
    --transition-fast: 0.2s ease;
    --transition-base: 0.3s ease;
    --transition-slow: 0.5s ease;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
    scroll-padding-top: 120px;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-primary);
    background-color: var(--background);
    color: var(--text-primary);
    line-height: 1.6;
    overflow-x: hidden;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* ===================================
   Hero Section
   =================================== */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    position: relative;
    overflow: hidden;
    background: radial-gradient(circle at 50% 50%, rgba(0, 120, 212, 0.1) 0%, transparent 50%);
    margin-left: 0;
}

.hero::before {
    content: '';
    position: absolute;
    top: -50%;
    left: -50%;
    width: 200%;
    height: 200%;
    background: repeating-linear-gradient(
        0deg,
        transparent,
        transparent 2px,
        rgba(80, 230, 255, 0.03) 2px,
        rgba(80, 230, 255, 0.03) 4px
    );
    animation: grid-move 20s linear infinite;
    pointer-events: none;
}

@keyframes grid-move {
    0% { transform: translate(0, 0); }
    100% { transform: translate(50px, 50px); }
}

.hero-content {
    position: relative;
    z-index: 2;
    text-align: center;
    max-width: 800px;
    padding: var(--spacing-lg);
    animation: fade-in-up 1s ease;
}

.hero-logo {
    margin-bottom: var(--spacing-lg);
    animation: float-gentle 3s ease-in-out infinite;
}

.logo-image {
    width: 400px;
    height: auto;
    filter: drop-shadow(0 10px 30px rgba(80, 230, 255, 0.3));
}

@keyframes float-gentle {
    0%, 100% { transform: translateY(0px); }
    50% { transform: translateY(-10px); }
}

@keyframes fade-in-up {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.hero-badge {
    display: inline-block;
    padding: var(--spacing-xs) var(--spacing-md);
    background: var(--gradient-primary);
    border-radius: 50px;
    font-size: 0.875rem;
    font-weight: 600;
    letter-spacing: 1px;
    text-transform: uppercase;
    margin-bottom: var(--spacing-md);
    animation: pulse 2s ease infinite;
}

@keyframes pulse {
    0%, 100% { opacity: 1; }
    50% { opacity: 0.8; }
}

.hero-title {
    font-family: var(--font-display);
    font-size: clamp(2.5rem, 8vw, 5rem);
    font-weight: 700;
    line-height: 1.1;
    margin-bottom: var(--spacing-md);
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.gradient-text {
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    display: inline-block;
}

.subtitle {
    font-family: var(--font-primary);
    font-size: clamp(1.25rem, 4vw, 2rem);
    font-weight: 300;
    color: var(--text-secondary);
}

.hero-description {
    font-size: 1.25rem;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-xl);
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
}

.hero-cta {
    display: flex;
    gap: var(--spacing-md);
    justify-content: center;
    flex-wrap: wrap;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-xs);
    padding: 1rem 2rem;
    border: none;
    border-radius: var(--radius-sm);
    font-family: var(--font-primary);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition-base);
    text-decoration: none;
    position: relative;
    overflow: hidden;
}

.btn::before {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    width: 0;
    height: 0;
    border-radius: 50%;
    background: rgba(255, 255, 255, 0.2);
    transform: translate(-50%, -50%);
    transition: width 0.6s, height 0.6s;
}

.btn:hover::before {
    width: 300px;
    height: 300px;
}

.btn-primary {
    background: var(--gradient-primary);
    color: var(--text-primary);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-glow);
}

.btn-secondary {
    background: transparent;
    color: var(--text-primary);
    border: 2px solid var(--primary-color);
}

.btn-secondary:hover {
    background: var(--primary-color);
    transform: translateY(-2px);
}

/* Floating Cards Animation */
.hero-graphic {
    position: absolute;
    inset: 0;
    pointer-events: none;
    opacity: 0.3;
}

.floating-card {
    position: absolute;
    width: 200px;
    height: 250px;
    background: var(--gradient-primary);
    border-radius: var(--radius-md);
    opacity: 0.1;
    animation: float 6s ease-in-out infinite;
}

.floating-card.card-1 {
    top: 10%;
    left: 10%;
    animation-delay: 0s;
}

.floating-card.card-2 {
    top: 60%;
    right: 15%;
    animation-delay: 2s;
}

.floating-card.card-3 {
    bottom: 15%;
    left: 20%;
    animation-delay: 4s;
}

@keyframes float {
    0%, 100% {
        transform: translateY(0) rotate(0deg);
    }
    25% {
        transform: translateY(-20px) rotate(5deg);
    }
    50% {
        transform: translateY(10px) rotate(-3deg);
    }
    75% {
        transform: translateY(-10px) rotate(3deg);
    }
}

/* ===================================
   Sidebar Navigation
   =================================== */
.sidebar {
    position: fixed;
    top: 0;
    left: 0;
    width: 280px;
    height: 100vh;
    background: var(--surface);
    border-right: 1px solid var(--border-color);
    overflow-y: auto;
    overflow-x: hidden;
    z-index: 999;
    transition: transform var(--transition-base);
    scrollbar-width: thin;
    scrollbar-color: var(--border-color) var(--surface);
}

.sidebar::-webkit-scrollbar {
    width: 6px;
}

.sidebar::-webkit-scrollbar-track {
    background: var(--surface);
}

.sidebar::-webkit-scrollbar-thumb {
    background: var(--border-color);
    border-radius: 3px;
}

.sidebar::-webkit-scrollbar-thumb:hover {
    background: var(--primary-color);
}

.sidebar.closed {
    transform: translateX(-100%);
}

.sidebar-header {
    padding: var(--spacing-lg);
    border-bottom: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    justify-content: space-between;
    position: sticky;
    top: 0;
    background: var(--surface);
    z-index: 1;
}

.sidebar-header h3 {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--text-primary);
    margin: 0;
}

.sidebar-close {
    display: none;
    background: none;
    border: none;
    color: var(--text-secondary);
    cursor: pointer;
    padding: var(--spacing-xs);
    border-radius: var(--radius-sm);
    transition: all var(--transition-fast);
}

.sidebar-close:hover {
    background: var(--surface-light);
    color: var(--text-primary);
}

.sidebar-nav {
    padding: var(--spacing-md) 0;
}

.sidebar-chapter {
    margin-bottom: var(--spacing-sm);
}

.sidebar-chapter-header {
    padding: var(--spacing-sm) var(--spacing-lg);
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    cursor: pointer;
    background: none;
    border: none;
    width: 100%;
    text-align: left;
    color: var(--text-primary);
    font-weight: 600;
    font-size: 0.9375rem;
    transition: all var(--transition-fast);
    border-left: 3px solid transparent;
}

.sidebar-chapter-header:hover {
    background: var(--surface-light);
    border-left-color: var(--primary-color);
}

.sidebar-chapter-icon {
    font-size: 1.25rem;
}

.sidebar-chapter-title {
    flex: 1;
}

.sidebar-chapter-toggle {
    transition: transform var(--transition-fast);
}

.sidebar-chapter.collapsed .sidebar-chapter-toggle {
    transform: rotate(-90deg);
}

.sidebar-sections {
    max-height: 1000px;
    overflow: hidden;
    transition: max-height var(--transition-base);
}

.sidebar-chapter.collapsed .sidebar-sections {
    max-height: 0;
}

.sidebar-section {
    padding: var(--spacing-xs) var(--spacing-lg) var(--spacing-xs) calc(var(--spacing-lg) + 2rem);
    display: block;
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 0.875rem;
    transition: all var(--transition-fast);
    border-left: 3px solid transparent;
}

.sidebar-section:hover {
    background: var(--surface-light);
    color: var(--text-primary);
    border-left-color: var(--secondary-color);
}

.sidebar-section.active {
    color: var(--secondary-color);
    background: linear-gradient(90deg, rgba(0, 120, 212, 0.15) 0%, rgba(80, 230, 255, 0.08) 100%);
    border-left-color: var(--secondary-color);
    font-weight: 600;
    box-shadow: inset 0 0 20px rgba(80, 230, 255, 0.1);
}

.menu-toggle {
    display: flex;
    position: fixed;
    top: var(--spacing-md);
    left: var(--spacing-md);
    z-index: 1001;
    background: var(--surface);
    border: 1px solid var(--border-color);
    color: var(--text-primary);
    padding: var(--spacing-sm);
    border-radius: var(--radius-sm);
    cursor: pointer;
    box-shadow: var(--shadow-md);
    transition: all var(--transition-fast);
    align-items: center;
    justify-content: center;
    width: 48px;
    height: 48px;
}

.menu-toggle:hover {
    background: var(--surface-light);
    border-color: var(--primary-color);
    transform: scale(1.05);
}

.sidebar-overlay {
    display: none;
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.5);
    z-index: 998;
    opacity: 0;
    transition: opacity var(--transition-base);
}

.sidebar-overlay.active {
    opacity: 1;
}

/* Main content with sidebar */
.main-content {
    margin-left: 280px;
    min-height: 100vh;
    transition: margin-left var(--transition-base);
}

.sidebar.closed ~ * .main-content,
body:has(.sidebar.closed) .main-content {
    margin-left: 0;
}

.content-wrapper {
    max-width: 1200px;
    margin: 0 auto;
    padding: var(--spacing-lg);
}

/* ===================================   Featured Showcase Section
   =================================== */
.featured-showcase {
    background: var(--background);
    padding: var(--spacing-2xl) var(--spacing-lg);
    position: relative;
    margin-left: 0;
}

.featured-showcase::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 1px;
    background: linear-gradient(90deg, transparent, var(--primary-color), transparent);
}

.showcase-container {
    max-width: 1400px;
    margin: 0 auto;
}

.showcase-header {
    text-align: center;
    margin-bottom: var(--spacing-2xl);
}

.showcase-title {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: var(--spacing-md);
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    letter-spacing: -0.02em;
}

.showcase-description {
    font-size: 1.125rem;
    color: var(--text-secondary);
    max-width: 600px;
    margin: 0 auto;
}

.showcase-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: var(--spacing-xl);
}

.showcase-card {
    background: var(--surface);
    border-radius: var(--radius-md);
    overflow: hidden;
    border: 1px solid var(--border-color);
    transition: all var(--transition-base);
    cursor: pointer;
}

.showcase-card:hover {
    transform: translateY(-8px);
    box-shadow: 0 12px 32px rgba(0, 120, 212, 0.2);
    border-color: var(--primary-color);
}

.showcase-image {
    position: relative;
    width: 100%;
    height: 220px;
    overflow: hidden;
    background: var(--surface-light);
}

.showcase-image img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: transform var(--transition-slow);
}

.showcase-card:hover .showcase-image img {
    transform: scale(1.1);
}

.showcase-info {
    padding: var(--spacing-lg);
}

.showcase-badge {
    display: inline-block;
    background: rgba(0, 120, 212, 0.1);
    color: var(--primary-color);
    padding: var(--spacing-xs) var(--spacing-sm);
    border-radius: var(--radius-sm);
    font-size: 0.75rem;
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.showcase-info h3 {
    font-size: 1.125rem;
    font-weight: 700;
    margin-bottom: var(--spacing-xs);
    color: var(--text-primary);
}

.showcase-info p {
    font-size: 0.875rem;
    color: var(--text-secondary);
    line-height: 1.6;
}

/* ===================================   Sticky Navigation (Hidden - replaced by sidebar)
   =================================== */
.sticky-nav {
    display: none;
}

.nav-container {
    max-width: 1400px;
    margin: 0 auto;
    padding: var(--spacing-md) var(--spacing-lg);
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: var(--spacing-md);
}

.nav-brand {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-weight: 600;
    font-size: 1.125rem;
    white-space: nowrap;
}

.nav-logo {
    width: 100px;
    height: auto;
    transition: transform var(--transition-base);
}

.nav-brand:hover .nav-logo {
    transform: rotate(360deg) scale(1.1);
}

.nav-brand-text {
    display: inline-block;
}

.cosmos-icon {
    font-size: 1.5rem;
}

.nav-chapters {
    display: flex;
    gap: var(--spacing-sm);
    flex-wrap: wrap;
    justify-content: center;
    flex: 1;
}

.nav-chip {
    padding: var(--spacing-xs) var(--spacing-md);
    border-radius: 50px;
    background: var(--surface-light);
    color: var(--text-secondary);
    font-size: 0.875rem;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition-base);
    border: 1px solid transparent;
    text-decoration: none;
    white-space: nowrap;
}

.nav-chip:hover {
    background: var(--primary-color);
    color: var(--text-primary);
    transform: translateY(-2px);
}

.nav-chip.active {
    background: var(--gradient-primary);
    color: var(--text-primary);
    border-color: var(--secondary-color);
}

.nav-progress {
    width: 100px;
    height: 4px;
    background: var(--surface-light);
    border-radius: 2px;
    overflow: hidden;
}

.progress-bar {
    height: 100%;
    background: var(--gradient-primary);
    width: 0%;
    transition: width var(--transition-base);
}

/* ===================================
   Main Content
   =================================== */
.main-content {
    max-width: 1400px;
    margin: 0 auto;
    padding: var(--spacing-2xl) var(--spacing-lg);
}

.chapter {
    margin-bottom: var(--spacing-2xl);
    animation: fade-in 0.6s ease;
}

@keyframes fade-in {
    from { opacity: 0; }
    to { opacity: 1; }
}

.chapter-header {
    text-align: left;
    margin-bottom: var(--spacing-xl);
    padding: var(--spacing-lg);
    padding-left: 80px;
    background: linear-gradient(135deg, rgba(0, 120, 212, 0.08) 0%, rgba(80, 230, 255, 0.04) 100%);
    border-radius: var(--radius-md);
    border-left: 4px solid var(--primary-color);
    position: relative;
}

.chapter:first-child .chapter-header {
    margin-top: 80px;
}

.chapter-icon {
    font-size: 2.5rem;
    margin-right: var(--spacing-sm);
    display: inline-block;
    vertical-align: middle;
}

.chapter-title {
    font-family: var(--font-primary);
    font-size: 2rem;
    font-weight: 700;
    margin-bottom: 0;
    color: var(--text-primary);
    display: inline-block;
    vertical-align: middle;
    letter-spacing: -0.02em;
}

.chapter-sections {
    display: grid;
    gap: var(--spacing-xl);
}

/* Section Card */
.section-card {
    background: var(--surface);
    border-radius: var(--radius-md);
    overflow: hidden;
    border: 1px solid var(--border-color);
    transition: all var(--transition-base);
    cursor: pointer;
    margin-bottom: var(--spacing-xl);
    position: relative;
}

.section-card.mobile-collapsed .section-content {
    max-height: 0;
    padding: 0;
    overflow: hidden;
    transition: all 0.4s ease;
}

.section-card.mobile-expanded .section-content {
    max-height: 2000px;
    padding: var(--spacing-lg) var(--spacing-xl);
    transition: all 0.4s ease;
}

.section-card:hover {
    transform: translateY(-4px);
    box-shadow: 0 8px 24px rgba(0, 120, 212, 0.15);
    border-color: var(--primary-color);
}

.section-image {
    position: relative;
    width: 100%;
    height: 500px;
    overflow: hidden;
    background: var(--surface-light);
    user-select: none;
    border-radius: var(--radius-md) var(--radius-md) 0 0;
}

.section-image canvas {
    width: 100%;
    height: 100%;
    object-fit: contain;
    transition: transform var(--transition-slow);
}

.section-card:hover .section-image canvas {
    transform: scale(1.05);
}

.image-overlay {
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    background: var(--gradient-overlay);
    padding: var(--spacing-md);
    transform: translateY(100%);
    transition: transform var(--transition-base);
}

.section-card:hover .image-overlay {
    transform: translateY(0);
}

.overlay-text {
    color: var(--text-primary);
    font-size: 0.875rem;
    font-weight: 500;
}

/* Watermark */
.image-watermark {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%) rotate(-45deg);
    font-size: 3rem;
    font-weight: 700;
    color: rgba(255, 255, 255, 0.05);
    pointer-events: none;
    user-select: none;
    white-space: nowrap;
    text-transform: uppercase;
    letter-spacing: 0.5rem;
}

.section-content {
    padding: var(--spacing-lg) var(--spacing-xl);
}

.section-title {
    font-size: 1.375rem;
    font-weight: 700;
    margin-bottom: var(--spacing-sm);
    color: var(--text-primary);
    letter-spacing: -0.02em;
}

.section-description {
    color: var(--text-secondary);
    margin-bottom: var(--spacing-sm);
    line-height: 1.6;
    font-size: 0.9375rem;
}

.key-points {
    background: rgba(0, 120, 212, 0.05);
    border-left: 3px solid var(--primary-color);
    border-radius: var(--radius-sm);
    padding: var(--spacing-md);
    margin-bottom: var(--spacing-md);
}

.key-points h4 {
    font-size: 0.875rem;
    font-weight: 700;
    margin-bottom: var(--spacing-sm);
    color: var(--text-primary);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.key-points ul {
    list-style: none;
    padding-left: 0;
}

.key-points li {
    padding: var(--spacing-xs) 0;
    padding-left: 1.5rem;
    position: relative;
    color: var(--text-secondary);
}

.key-points li::before {
    content: '→';
    position: absolute;
    left: 0;
    color: var(--primary-color);
    font-weight: 700;
}

.learn-more-link {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-xs);
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 600;
    transition: all var(--transition-fast);
}

.learn-more-link:hover {
    color: var(--secondary-color);
    gap: var(--spacing-sm);
}

/* ===================================
   Modal
   =================================== */
.modal {
    position: fixed;
    inset: 0;
    z-index: 1000;
    display: none;
    align-items: center;
    justify-content: center;
    padding: var(--spacing-md);
}

.modal.active {
    display: flex;
}

.modal-backdrop {
    position: absolute;
    inset: 0;
    background: rgba(15, 15, 30, 0.95);
    backdrop-filter: blur(10px);
    animation: fade-in 0.3s ease;
}

.modal-content {
    position: relative;
    z-index: 1;
    background: var(--surface);
    border-radius: var(--radius-lg);
    max-width: 1200px;
    width: 100%;
    max-height: 90vh;
    overflow: hidden;
    border: 1px solid var(--border-color);
    animation: slide-up 0.4s ease;
}

@keyframes slide-up {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.modal-close {
    position: absolute;
    top: var(--spacing-md);
    right: var(--spacing-md);
    z-index: 2;
    width: 40px;
    height: 40px;
    border-radius: 50%;
    background: var(--surface-light);
    border: none;
    color: var(--text-primary);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all var(--transition-base);
}

.modal-close:hover {
    background: var(--primary-color);
    transform: rotate(90deg);
}

.modal-body {
    display: grid;
    grid-template-columns: 1.2fr 1fr;
    max-height: 90vh;
    overflow-y: auto;
}

.modal-image-container {
    background: var(--surface-light);
    display: flex;
    align-items: center;
    justify-content: center;
    padding: var(--spacing-lg);
    position: relative;
    user-select: none;
    overflow: auto;
    cursor: grab;
}

.modal-image-container.dragging {
    cursor: grabbing;
}

.modal-image-container canvas {
    max-width: 100%;
    max-height: 70vh;
    object-fit: contain;
    transition: transform 0.2s ease;
    transform-origin: center center;
}

/* Zoom Controls */
.zoom-controls {
    position: absolute;
    bottom: var(--spacing-md);
    right: var(--spacing-md);
    display: flex;
    gap: var(--spacing-xs);
    background: rgba(26, 26, 46, 0.95);
    backdrop-filter: blur(10px);
    padding: var(--spacing-xs);
    border-radius: var(--radius-sm);
    border: 1px solid var(--border-color);
    align-items: center;
    z-index: 10;
}

.zoom-btn {
    width: 36px;
    height: 36px;
    border-radius: var(--radius-sm);
    background: var(--surface-light);
    border: 1px solid var(--border-color);
    color: var(--text-primary);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all var(--transition-fast);
}

.zoom-btn:hover {
    background: var(--primary-color);
    border-color: var(--secondary-color);
    transform: translateY(-2px);
}

.zoom-btn:active {
    transform: translateY(0);
}

.zoom-level {
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--text-secondary);
    min-width: 50px;
    text-align: center;
    padding: 0 var(--spacing-xs);
}

.modal-info {
    padding: var(--spacing-xl);
    overflow-y: auto;
}

.modal-info h2 {
    font-size: 2rem;
    margin-bottom: var(--spacing-md);
    color: var(--text-primary);
}

.modal-info p {
    color: var(--text-secondary);
    line-height: 1.8;
    margin-bottom: var(--spacing-lg);
}

.modal-key-points {
    background: var(--background);
    border-radius: var(--radius-md);
    padding: var(--spacing-md);
    margin-bottom: var(--spacing-lg);
}

.modal-key-points h4 {
    font-size: 1.125rem;
    margin-bottom: var(--spacing-md);
    color: var(--secondary-color);
}

.modal-key-points ul {
    list-style: none;
    padding-left: 0;
}

.modal-key-points li {
    padding: var(--spacing-sm) 0;
    padding-left: 2rem;
    position: relative;
    color: var(--text-secondary);
}

.modal-key-points li::before {
    content: '✓';
    position: absolute;
    left: 0;
    color: var(--success-color);
    font-weight: 700;
    font-size: 1.25rem;
}

/* ===================================
   Footer
   =================================== */
.footer {
    background: var(--surface);
    border-top: 1px solid var(--border-color);
    margin-top: var(--spacing-2xl);
}

.footer-content {
    max-width: 1400px;
    margin: 0 auto;
    padding: var(--spacing-2xl) var(--spacing-lg);
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-xl);
}

.footer-section h3 {
    font-size: 1.5rem;
    margin-bottom: var(--spacing-md);
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.footer-section h4 {
    font-size: 1.125rem;
    margin-bottom: var(--spacing-md);
    color: var(--secondary-color);
}

.footer-section p {
    color: var(--text-secondary);
    line-height: 1.8;
}

.footer-section ul {
    list-style: none;
    padding: 0;
}

.footer-section li {
    margin-bottom: var(--spacing-sm);
}

.footer-section a {
    color: var(--text-secondary);
    text-decoration: none;
    transition: color var(--transition-fast);
}

.footer-section a:hover {
    color: var(--primary-color);
}

.github-link {
    display: inline-flex;
    align-items: center;
    font-weight: 600;
}

.github-link:hover {
    color: var(--secondary-color) !important;
}

.footer-note {
    font-size: 0.875rem;
    color: var(--text-muted);
}

.footer-bottom {
    border-top: 1px solid var(--border-color);
    padding: var(--spacing-lg);
    text-align: center;
    color: var(--text-muted);
}

/* ===================================
   Responsive Design
   =================================== */
@media (max-width: 1024px) {
    .modal-body {
        grid-template-columns: 1fr;
    }
    
    .modal-image-container canvas {
        max-height: 50vh;
    }
}

@media (max-width: 768px) {
    .sidebar {
        transform: translateX(-100%);
        box-shadow: none;
    }
    
    .sidebar.open {
        transform: translateX(0);
        box-shadow: var(--shadow-lg);
    }
    
    .sidebar.closed {
        transform: translateX(-100%);
    }
    
    .sidebar-close {
        display: block;
    }
    
    .menu-toggle {
        display: flex;
    }
    
    .sidebar-overlay.active {
        display: block;
    }
    
    .main-content {
        margin-left: 0;
    }
    
    .hero,
    .featured-showcase {
        margin-left: 0;
    }
    
    .content-wrapper {
        padding: var(--spacing-lg) var(--spacing-md);
    }
    
    .hero-cta {
        flex-direction: column;
        align-items: center;
    }
    
    .hero-title {
        font-size: 2rem;
    }
    
    .logo-image {
        width: 200px;
    }
    
    .showcase-title {
        font-size: 1.75rem;
    }
    
    .showcase-grid {
        grid-template-columns: 1fr;
        gap: var(--spacing-lg);
    }
    
    .showcase-image {
        height: 180px;
    }
    
    .section-image {
        height: 450px;
    }
    
    .section-card {
        margin-bottom: var(--spacing-md);
    }
    
    .section-content {
        padding: var(--spacing-md);
    }
    
    .section-card.mobile-collapsed .section-image {
        height: 500px;
    }
    
    .section-card.mobile-collapsed::after {
        content: 'Tap to view details';
        position: absolute;
        bottom: var(--spacing-md);
        left: 50%;
        transform: translateX(-50%);
        background: rgba(0, 120, 212, 0.9);
        color: white;
        padding: var(--spacing-xs) var(--spacing-md);
        border-radius: var(--radius-sm);
        font-size: 0.875rem;
        font-weight: 600;
        pointer-events: none;
        z-index: 10;
        animation: pulseButton 2s infinite;
    }
    
    @keyframes pulseButton {
        0%, 100% { opacity: 1; transform: translateX(-50%) scale(1); }
        50% { opacity: 0.8; transform: translateX(-50%) scale(1.05); }
    }
    
    .nav-container {
        flex-direction: column;
        gap: var(--spacing-sm);
    }
    
    .nav-chapters {
        order: 2;
        width: 100%;
    }
    
    .nav-progress {
        order: 3;
        width: 100%;
    }
    
    .section-image {
        height: 300px;
    }
    
    .chapter-header {
        padding-left: var(--spacing-md);
    }
    
    .chapter-title {
        font-size: 2rem;
    }
    
    .footer-content {
        grid-template-columns: 1fr;
    }
}

/* ===================================
   Accessibility
   =================================== */
.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border-width: 0;
}

/* Focus styles */
a:focus-visible,
button:focus-visible {
    outline: 2px solid var(--secondary-color);
    outline-offset: 2px;
}

/* Reduced motion */
@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}

/* Print styles */
@media print {
    .hero,
    .sticky-nav,
    .footer,
    .modal {
        display: none !important;
    }
    
    body {
        background: white;
        color: black;
    }
    
    .section-card {
        break-inside: avoid;
        page-break-inside: avoid;
    }
}